1. Field of the Invention
Embodiments of the present invention generally relate to handling and transfer semiconductor substrates during semiconductor processing. More particularly, embodiments of the present invention relate to end effectors for use with a robot for handling semiconductor substrates.
2. Description of the Related Art
The use of robot arms is a well established manufacturing expedient in applications where human handling is inadequate and/or undesired. For example, in the semiconductor manufacturing, robot arms are used to handle substrates during and between various steps to provide speed and reduce contamination.
A substrate handler used in semiconductor processing generally includes one or more end effectors, also known as a robot blade or a carrier, attached to a robot arm. The end effectors are configured to support a substrate during substrate transferring. For an integrated semiconductor processing system, a robot arm is generally disposed in a transfer chamber having facets to accommodate a plurality of processing chambers, and loading/unloading ports. During processing, the robot arm in the transfer chamber first loads a substrate to the end effector from a loading port. After retrieving the substrate to the transfer chamber, the robot arm feeds the substrate to a processing chamber connected to the transfer chamber. The robot arm drops the substrate on a substrate support in the processing chamber and retrieves the end effector. When the process is completed in the processing chamber, the robot arm is employed to retrieve the substrate from the substrate chamber and to shuttle the substrate to another processing chamber for the next processing step.
Some common transfer chambers have facets to accommodate four to six processing chambers. The processing chambers may include rapid thermal processing (RTP) chambers, physical vapor deposition (PVD) chambers, chemical vapor deposition (CVD) chambers, and etch chambers.
FIG. 1 schematically illustrates a substrate handler 10 configured for handling substrates in a transfer chamber. The substrate handler 10 includes two end effectors 14 attached to an arm assembly 16 attached to a rotating portion 18. During transferring, a substrate sits on the end effector 14. The end effector 14 has a fixed end 27 attached to a mounting interface 28 of the arm assembly 16, and a free end 29 configured to support a substrate thereon. The free end 29 may have a substrate sensing hole 15 configured to let through a sensor beam used to detect presence of a substrate. The arm assembly 16 moves the end effectors 14 radially outward from and inward to the substrate handler 10 to insert a substrate into or retrieve a substrate from a processing chamber.
The end effectors of prior art have several limitations. First, the end effector exhibits a droop (i.e. a tip-to-tail deflection) due to natural material compliance and weight of the substrate. Droop becomes more pronounced as the end effector becomes thinner to access densely packed substrates and as the size of the substrates become larger. FIG. 2A schematically illustrates a partial sectional side view of the end effector 14 without a substrate. FIG. 2B is a schematic sectional side view of the end effector 14 with a substrate 30 loaded thereon. An increased droop in the end effector 14 is shown due to weight of the substrate 30 positioned on the end effector 14. After the substrate 30 is loaded, the free end droops to an angle α.
High precision is critical in semiconductor processing. It is critical for a substrate handler, therefore, an end effector, to have high precision alignment. The end effectors are generally aligned and tightly secured on the robot arm to prevent any unwanted moves, which may cause distortion due to thermal expansion. During some high temperature processes, such as rapid thermal annealing, the end effector may need to transfer a hot substrate or to operate in a hot chamber. The temperature may be up to 350° C. The tightly secured end effector may become deformed due to thermal expansion at such high temperature. FIG. 3 schematically illustrates a top view of the end effector 14 secured on the mounting interface 28 of the arm assembly 16. The fixed end 27 of the end effector 14 is snuggly fitted between sidewalls 31 of the mounting interface 28 to prevent any rotations. When the end effector 14 is made from material having a larger thermal expansion rate than the material of the mounting interface 28, the fixed end 27 of the end effector 14 may exhaust any tolerance in seams 32 and become deformed. Additionally, drooping also increases at higher temperature.
Therefore, there is a need for apparatus and methods for transfer a substrate at high temperature without drooping or otherwise deforming.